ETYM as. naegel, akin to Dutch nagel, Old High Germ. nagal, German nagel, Icel. nagl, nail, nagli nail, Swed. nagel nail, Dan. nagle, Goth. ganagljan to nail, Lith. nagas nail, Russ. nogote, Latin unguis, Skr. nakha.
In biology, a hard, flat, flexible outgrowth of the digits of primates (humans, monkeys, and apes). Nails are composed of keratin.
The horny plate covering and protecting the backs of the fingertips; fingernail.

Old measure of two and a quarter inches
A long, pointed piece of metal, usually topped with a flatter surface (or) that is hammered into materials as a fastener.
A former unit of length for cloth equal to 1/16 of a yard.

1. To attach something somewhere by means of nails
2. To conclude something successfully, decisively